JPH07147503A - Dielectric filter - Google Patents

Abstract

PURPOSE:To obtain the multi-frequency filter having a resonance frequency other than a substantial resonance frequency by connecting a capacitor or an inductor to >= one resonator respectively via a changeover switch. CONSTITUTION:A series circuit comprising a capacitor C4 and an on/off switch S4 is connected between a circuit connecting point 3 of a dielectric resonator R1 and ground, and a series circuit comprising a capacitor C5 and an on/off switch S5 is connected between a circuit connecting point 4 of a dielectric resonator R2 and ground. When the switches S4, S5 are open, a combined resonance frequency of the resonators R1, R2 is f0. When the switches S4, S5 are closed, the circuit C4 is connected in parallel with the resonator R1 and the circuit C5 is X connected in parallel with the resonator R2 respectively and its synthesis resonance frequency is f1. Thus, two filter functions are obtained by changeover of the switches.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a dielectric filter in which a capacitor or an inductor is connected in parallel to a dielectric resonator via a changeover switch, and the changeover switch is changed over to obtain multiple frequencies.

[0002]

2. Description of the Related Art A conventional dielectric filter having a two-stage BPF is shown in FIG. R1 and R2 are resonators,
C is the coupling capacitance. Further, in the conventional duplex type dielectric filter, as shown in FIG. 8, it is composed of a Tx side dielectric filter 11, an Rx side dielectric filter 12, and matching circuits 13 and 14. C is a coupling capacitance, and R1 to R4 are resonators.

[0003]

However, in the conventional BPF dielectric filter, as shown in FIG. 9, the pass characteristic of FIG. 7 is a BPF characteristic having one center frequency f ₀ . Therefore, it was not possible to freely select other center frequencies.

Further, the conventional duplex type dielectric filter requires two BPF circuits of the Tx side dielectric filter 11 and the Rx side dielectric filter 12, and matching circuits 13 and 14 for matching them. there were.

Therefore, according to the present invention, at least one capacitor or inductor is connected in parallel to at least one dielectric resonator having one resonance frequency via a switch to generate another resonance frequency, and Alternatively, it is an object to provide a dielectric filter capable of selecting multiple frequencies by switching the inductor with a switch.

[0006]

The present invention provides a dielectric filter circuit comprising at least one or more dielectric resonators, wherein at least one or more dielectric resonators are provided with at least one or more capacitors or inductors. It is a dielectric filter characterized by being connected in parallel via a switch and obtaining multiple frequencies by switching the switch.

[0007]

According to the present invention, since at least one capacitor or inductor is connected in parallel to at least one dielectric resonator through a changeover switch,
By switching the switch, the capacitor or the inductor is connected in parallel with the dielectric resonator, and multiple frequencies of the original resonant frequency of the dielectric resonator and the resonant frequency of the parallel connection of the capacitor or the inductor can be obtained.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows a first embodiment. R1,
R2 is a λ / 4 dielectric resonator, and coupling capacitors C1 and C
2 is a two-stage BPF dielectric filter circuit coupled by C3. In addition, 1 is an input terminal and 2 is an output terminal.
Between the circuit connection point 3 of the dielectric resonator R1 and the ground,
A series circuit of a capacitor C4 and an on / off switch S4 is connected. Further, between the circuit connection point 4 of the dielectric resonator R2 and the ground, a capacitor C5 and an on / off switch are connected.
A series circuit with the switch S5 is connected. The switches S4 and S5 are interlocked as shown by the dotted line.

Although this embodiment is as described above, the operation will be described below. When the switches S4 and S5 are off as shown, the combined resonance frequency of the resonators R1 and R2 is
As shown in, the f _0. When the switches S4 and S5 are on, the capacitor C4 is connected in parallel to the resonator R1 and the capacitor C5 is connected in parallel to the resonator R2, and the combined resonance frequency thereof is f1. Thus, by switching one resonator filter circuit with a switch, it can be used as two filters.

FIG. 3 shows a circuit in which the input / output terminals 1 and 2 of the dielectric filter circuit of FIG. That is, the input side circuit changeover switch S is connected to the input terminal 1 of the filter circuit.
6, and the output terminal 2 of the dielectric filter circuit, the output side circuit changeover switch S7 is provided in conjunction with the switch S4 and the switch S5, can be used as a duplexer. The input side circuit changeover switch S6 may be omitted depending on the circuit condition. FIG. 4 shows a second embodiment. In the resonator R1, between the circuit connection point 3 of the resonator R1 and the ground, two capacitors C4 and C5 having different capacities (capacity size is C4 <C5).
Are connected in parallel via a three-contact changeover switch S8.

The present embodiment has the above-mentioned configuration, and its operation will be described below. Since only the resonator R1 is connected to the ground when the switch S8 is off,
The center frequency f ₀ of the resonator R1 is output from the output terminal 2 as shown in FIG. Switch S8 is capacitor C
When it is connected to the fourth side, a capacitor C4 is connected in parallel to the resonator R1 and its parallel resonance frequency f1
Is output from the output terminal 2 as shown in FIG. Further, when the switch S8 is connected to the side of the capacitor C5, the capacitor C5 is connected in parallel to the resonator R1, and its parallel resonance frequency f2 is as shown in FIG.
It is output from the output terminal 2. Therefore, in the embodiment shown in FIG. 4, the frequency can be switched in three stages.

FIG. 6 shows the output terminal 2 of the filter circuit of FIG.
In addition, a three-contact changeover switch S9 is connected to distribute to the branching circuit in the subsequent stage. In addition, this 3
The contact changeover switch S9 is interlocked with the switch S8 as shown by the dotted line.

The present invention has the above-mentioned structure, and in the above embodiment, the case of the two-stage BPF is shown.
It is also applied in the multi-stage PF. Also, the resonator is λ / 4
However, it may be λ / 2. Moreover, the capacitor of the series circuit may be an inductor. In this case, the composite resonance frequency shifts to the higher side. Further, not only BPF but also BEF is possible. Further, the dielectric resonator is not limited to the discrete type, but may be a block type.

[0014]

According to the present invention, at least one or more capacitors or inductors are connected in parallel to at least one or more dielectric resonators via a changeover switch, so that the capacitors or inductors can be switched by changing over the switches. Is connected in parallel with the dielectric resonator, and a multi-frequency filter having a resonance frequency of a parallel connection of a capacitor or an inductor can be obtained in addition to the original resonance frequency of the dielectric resonator.

[Brief description of drawings]

FIG. 1 is a dielectric filter circuit diagram according to an embodiment of the present invention.

FIG. 2 is a frequency amplitude characteristic diagram of FIG.

FIG. 3 is a derivative diagram of the embodiment of FIG.

FIG. 4 is a dielectric filter circuit diagram according to another embodiment of the present invention.

FIG. 5 is a frequency amplitude characteristic diagram of FIG.

FIG. 6 is a derivative diagram of the embodiment of FIG.

FIG. 7 is a conventional dielectric filter circuit diagram.

FIG. 8 is another conventional dielectric filter circuit diagram.

FIG. 9 is a frequency amplitude characteristic diagram of FIG. 7.

[Explanation of symbols]

 C1 to C3 Coupling capacitor 1 Input terminal 2 Output terminal 3, 4 Circuit connection point S4, S5, S6 switch S6 Input side circuit changeover switch S7 Output side circuit changeover switch S8, S9 3 contact changeover switch

Claims (1)

[Claims] 1. A dielectric filter circuit comprising at least one or more dielectric resonators, wherein at least one or more dielectric resonators are connected in parallel with at least one or more capacitors or inductors, A dielectric filter characterized by obtaining multiple frequencies by switching switches.